[time-nuts] HP5335A GPIB questions.

Bill Byrom time at radio.sent.com
Sat Mar 21 23:42:09 EDT 2015

Luke, the HP5335A was introduced in around 1980 and has an early
(pre-IEEE-488.2) HP implementation of IEEE-488 which requires a
terminator character at the end of each string. According to the manual,
this terminator can be a comma, semicolon, space, carriage return, or
line feed character.

Later products (after about 1987) usually required a terminator of CR
(carriage return), LF (line feed), or the hardware EOI (end or identify)
termination method.

In addition to the terminator character, your GPIB interface needs to
change the bus transfer direction by unaddresing the HP5335A as a
listener and making it a talker. Early IEEE-488 implementations in the
late 1970's (IEEE-488 was introduced in 1975) and early 1980's often
required explicit computer commands to assert and release the talk and
listen commands, but by about 1990 the software commands usually
performed these low level details for you automatically.

So I suggest looking at the documentation for your GPIB interface and
making sure you use a terminator character (from the list above) instead
of only the EOI method of terminating commands, since I think the
HP5335A will ignore the EOI line. Most GPIB interfaces in the past 20
years can be set to send a LF (ASCII 10 hex) character along with the
EOI line transition to indicate the end of a command, and that should
work. These old GPIB devices use very simple short cryptic commands, but
they don't follow the later IEEE-488.2 and SCPI conventions. I'm sure
you will be able to get this to work with the right configuration of
termination character and talk/listen turnaround.

Bill Byrom N5BB

On Sat, Mar 21, 2015, at 09:24 PM, Luke Mester wrote:
> I recently bought a HP5335A counter and have some questions about
> operating the instrument with GPIB.
> I expect that a lot of time nuts are using this instrument and may be
> able to help. Please excuse me if this is a stupid question. This is
> my first GPIB instrument.
> After each GPIB command that I send I've found that I then need to
> send an RE (reset) command. If I Don't send RE the instrument takes no
> readings and has a blank display. For example I send FN9 to select
> period and get no readings until RE is sent. Is this normal?
> I'm currently talking to it with a USB to GPIB adapter and a terminal
> program.
> Since I had no idea if the GPIB interface was functional I didn't want
> to buy an expensive GPIB adapter. I build the cheapest GPIB adapter
> that I could find on the internet. It's possible that this is causing
> problems.
> It emulates a Prologix adapter. Here is a link if you're interested.
> HTTP://http://www.dalton.ax/gpib/ I've found that this adapter does
> not properly report the serial control line status. Because of this,
> Timelab won't detect the GPIB adapter.
> You can get Timelab to work if you choose the "Acquire from counter in
> talk only mode" option.
> --
> Luke Mester http://mesterhome.com/
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